Images and design patterns may be placed upon substrates by various methods, including organic solvent-based ink jet printing. Ink jet printing is the process of placing predetermined quantities of a solvent-based material (“ink”) containing a colorant upon a substrate in predetermined target matrix zones of a substrate. Solvent-based ink jet printing employs organic carbon-containing solvents to carry colorants, or ink, to the surface of printing substrates. Substrates commonly employed in solvent-based ink jet printing include nonporous plastic films, plastic sheets, and coated fabric. However, many of such substrates are impervious to air, nonporous, undesirably stiff, and relatively expensive.
Efforts have been made to employ flexible or porous textile substrates for solvent-based ink jet printing. Numerous applications exist for such products, including graphic artwork, signage, banners, flags, and various types of decorative textile materials. It also would be desirable to form a repellant surface on such printed materials, to render the surface of such materials impervious or resistant to liquids, including water and oily staining substances.
Unfortunately, efforts to apply high quality solvent-based ink jet images to flexible fibrous textile substrates have met with only limited success. Porous textiles, when subjected to solvent-based inks, often reveal a poor quality printed image. Organic solvents used to carry the ink to the textile substrate surface often undesirably wick into the porous structure of the textile. Such wicking results in undesirable ink feathering and relatively poor color density.
Ionic-based chemical treatments have been used in some instances to remedy deficiencies in aqueous-based ink jet printing. Some treatments fix in place the ink or colorant upon the surface of fibers in the textile, resulting in less undesirable ink expansion, and a sharper printed image. However, such ionic-based treatments are not readily suitable for solvent-based inks in part because colorants employed in organic solvent-based inks usually are not highly ionic. Therefore, ionic-based chemical treatments are not well suited to solve the problem of poor print quality in solvent-based printing systems.
For example, FIG. 2A shows a solvent-based printed textile 25 with an undesirably blurred image. Such an undesirable image is due in part to the nature of the textile coating 26 applied to the textile 25 which has an undesirably low degree of repellancy. The undesirably low repellancy of the coating 26 is evident by observing the low contact angle θ of the solvent droplet 27 upon the textile 25, as seen in FIG. 2. FIG. 2 shows the solvent-based ink droplet 27 just prior to its evolution into the textile 25. FIG. 2A therefore illustrates an undesirably broad ink deposition resulting from deposition of the droplet 27 of FIG. 2 into textile 25, resulting in a blurred printed image. The organic solvent of solvent-based ink droplet 27 shown of FIG. 2 has left ink deposits 28-29 (FIG. 2A) well beyond the target printing zone 30, leaving a blurred image upon textile 25.
FIG. 3A illustrates a solvent-based printed textile 35 with a dull image. The dull image is caused in part by the undesirable deposition of ink 38 deep into the textile 35 well below the upper surface 39 of the coated textile 35. FIGS. 3-3A illustrate the result of excessive repellancy exhibited by the repellant coating 36 upon the textile 35. The solvent-based ink droplet 37 (see FIG. 3) which experiences excessive repellancy has a high contact angle θ which is greater than 90 degrees. When ink within such a droplet 37 eventually merges (usually by heat) into the textile 35, an undesirably deep deposition of ink 38 is experienced, forming a dull image upon textile 35.
A composition and method for treating a porous textile substrate to render the substrate capable of receiving organic solvent-based ink in producing a sharp and vivid image would be very desirable. A porous substrate having a repellant coating which reveals a desirable degree of repellancy with an appropriate solvent contact angle, enabling production of a high quality sharp and bright printed image, is needed. It would be very helpful if such a printed substrate were capable of repelling liquids such as water and oily staining substances.